The present invention relates to subject analysis methods and systems in general and, more particularly, to a method and apparatus for particle analysis which utilizes color algebra and image processing techniques.
The preferred embodiment for this continuation in part is almost identical to that in the original application, now U.S. Pat. No. 3,851,156. However, to avoid confusion and numerous referencing, much of the descriptive material in the original application will be repeated here.
The need for an accurate, fast and relatively inexpensive system for analyzing particulate matter entrained in a gas or liquid exists in many fields of current technology. For example, recent activities in the area of pollution analysis and control have emphasized the need for a means for particle identification, classification and morphology analysis. A similar need also exists in the field of medical technology for automating labor intensive medical laboratory procedures, such as blood analysis.
The recent spiraling rise of medical care cost have raised the hope that these costs could be reduced by the application of automation technology to the labor intensive procedures used in the medical field. One of the most fundamental tests performed in the most cursory examination or treatment of a patient is blood analysis. Blood has three major particle components: red blood cells (RBC), white blood cells (WBC) and platelets, suspended in a fluid (plasma). An analysis of the relative and absolute quantities of these particles, and additional information regarding their morphology (form and structure) provide considerable insight into the state of health of the patient.
At the present time, several companies have successfully developed and marketed instruments for automated blood analysis. Technion's SMA system for plasma analysis and Hemalog System for cell analysis, and Coulter Electronics' Model S cell counter are well known examples. Using different technologies, the Hemalog and Coulter S generally provide a cost-competitive count of the various particle constituents present in a blood sample. The basic concept, common to both techniques, involves flowing a thin column of diluted blood past a sensor which detects whether a solid particle is present in the liquid medium. This concept, commonly called "flow-through", provides a count of the particles present, but does not provide any qualitative information regarding the identity of these particles or of their morphology.
Therefore, it is necessary to pre-segregate the sample to determine whether the instrument is counting a RBC or a WBC. These two types of cells have significantly different chemical properties, so they can be separated relatively easily. However, it is not possible to further automatically differentiate these cells according to their individual morphological differences using currently available commercial technology.
Nevertheless, such a differentiation is extremely important in about 25 percent of all hospital patients, and it is highly desirable in 50 percent of the patients. This is particularly true of the numerous types of WBC's whose relative concentration and individual morphology are extremely important. Of lesser importance, but still significant is the detection of abnormal red cell morphology. These measurements, commonly known as the "Differential" count, are currently performed by manual labor.
There are two basic approaches to differentiating a single cell by morphology; a direct or pattern recognition approach and, an indirect approach. The latter relies on there being indirect signatures of chemical differences which have a high degree of correlation with the direct signature of morphological differences in the basic WBC's types. Technion's Hemalog-D, employs this approach, using enzymatic stains as the chemical signature to separate five basic WBC types.
As in all indirect techniques, there are both theoretical and practical sources of error. For example, abnormal variations within any of the five basic WBC groups cannot be detected. In a high risk hospital population, 10 to 20 percent of the patients may have relatively normal distribution among the five chemical groups, but still have morphological abnormalities indicative of a pathology. In other words, the morphological/chemical correlation is incomplete, resulting in false negatives, the most serious type of error. Furthermore, a percentage of any healthy population will have unusually low enzyme levels with no accompanying morphological abnormalities or clinical symptoms thus resulting in uneconomical false positives. In addition, the important RBC morphology is not provided by the indirect technique.
In the direct approach, the morphology of the particles or cells is examined directly using computer pattern recognition techniques. Performing the blood cell differential measurement using pattern recognition techniques is within the current state of the Corning, Geometric Data Corp., and Coulter have announced instruments using these techniques. However, these early instruments, in order to be practical from a cost standpoint utilize designs which are too slow and do not automate the analysis of abnormal white blood cells or red blood cells. The same general problems exist in other fields of technology employing particle analysis techniques.
It is, accordingly, a general object of the invention to provide an improved system for subject analysis.
It is a specific object of the invention to provide a particle analysis system which employs color algebra in conjunction with image processing techniques to analyze scene regions.
It is another specific object of the present invention to provide, as one embodiment thereof, a commercially feasible automated blood differential measurement system.
It is a further object of the present invention to employ color algebra techniques which permit the use of simplified algorithms to analyze scene regions.
It is still a further object of the present invention to provide an automated blood differential measurement system which employs scanning and data processing components which, in conjunction with color algebra techniques, drastically reduce both the computer capacity requirement and the processing time.
It is a feature of the present invention that the automated blood differential measurement system embodiment provides increased accuracy over existing systems due to the inherent superiority of a direct measurement technique over an indirect measurement technique together with the additional ability to make finer distinctions between WBC's in any one of the five basic types, the ability to recognize abnormal v. normal morphology; the ability to provide RBC measurements; and the ability to distinguish between cell regions and other scene regions.
It is still another feature of the blood analysis embodiment of the present invention that conventional blood staining procedures can be employed with the color algebra technique of the invention.